The experiments are designed to test the hypothesis that the hippocampus (and not other brain systems) is selectively involved in the processes of working memory (and not other types of memory). The working memory hypothesis makes two predictions. First, rats with lesions of the hippocampal system should exhibit a severe impairment in the working memory components of a task, but be able to perform the reference memory components as well as normal rats. Second, electrophysiological recording from the hippocampus should indicate that hippocampal neurons are selectively active during tasks that require working memory. Experiments using both lesions and electrophysiological recording are proposed to evaluate the validity of these predictions. The results will provide information about the neuroanatomical mechanisms of normal memory, and the neuropathology responsible for human amnesia.